7mm SAUM Wildcat!

I am going to build a long range hunting rifle in some sort of 7mm. I am set on compmnents: Lawton 7000 SA, 30" Kreiger 1-9 twist, AI stock. My dillemma comes with the 7SAUM and loading 180 Berger's long. (I want to use an AI stock and magazines and obviously they won't work this way.)
I had also noticed that a .284 Shehane will do basically the same velocities but is even a tad longer when loaded long. This got me thinking wildcat. My idea was to take the proportions of a 6mm Dasher and push them out to a SAUM case.
When I did these calcs. I found some interesting things:
- This gave me almost identical volumes to a .284 Shehane
- The start of the shoulder was only slightly shorter than a standard SAUM

So, I thought why re-invent the wheel? Keep the lower (below the shoulder) part of the case the same, and put a 40' shoulder on it. With this combination it should have a slightly larger capacity than the Shehane but not much. This smaller volume should be more efficient than the SAUM or WSM. I am hoping that with about 56 grains of H4831sc it will consistently reach the 3000-3050 fps velocity node.

Advantages:

- This will easily fit into an AI mag. with a 180 Berger loaded long
- with the 40' shsoulder I think that t will give slightly better vels. with similar charges as the Shehane
- With a similar powder load to the Shehane I was thinking that the barrell life should be similar (everything else being the same).

I have drawn up a reamer for Mr. Kiff but am needing some suggestions on some things I didn't really know. (the question marks on the print) I was also wondering if someone could run this through QUICK LOAD and see what it spits out.

I also have not had a chance to measure any bullets yet so if anyone knows the bearing surface lengths of some bullets and could post them that would be great so that I can finalize the freebore length. As you may notice this is basically a SAAMI chamber with a 40' shoulder and a slightly tighter neck.

Valid point, I was, more than anything, trying to make a more efficient cartridge.
The ultimate goal here is to get WSM velocities while using the same amount of powder as the Shehane. The fact that all this would fit in a SA is just an added bonus!
Also, I forgot to mention, the body has also been shortened .100 this should give an overall length of 2.80" or so. And about 67.5 grains of H2O capacity.

Sooo, I thought why not straighten out the case a bit? This reamer would give the same body taper as a WSM and add about a 1.5 grain of H2O cap. Has anyone had any problems extracting their WSM's or does anyone think this could cause a problem?

I don't know anything about your action, but I think the cartridge is a great choice(minus available brass).
And I'll check with the ole lady, but I'm thinkin you should consider length AND girth for your magnum diameter cartridge.
Otherwise you may not reach the desired potential before extraction issues.
Be sure you have sufficient barrel steal around the chamber(magnum barrel tenon) w/resp to a working design(like Savage WSM barrels).

Also check to be sure you can eject from your port.
While a SAUM is shorter than other magnums, it's not a short cartridge.

My gs did quite a little bit of work to get the 160 AB to fit in the sa Browning mag. He lengthened a couple of mags .125 each and notched the ejection port to eject a loaded cartridge. If I had to do it again I might choose a Browning long action.

Valid point, I was, more than anything, trying to make a more efficient cartridge.
The ultimate goal here is to get WSM velocities while using the same amount of powder as the Shehane. The fact that all this would fit in a SA is just an added bonus!
Also, I forgot to mention, the body has also been shortened .100 this should give an overall length of 2.80" or so. And about 67.5 grains of H2O capacity.

Another reason for the short action is detachable box mag capacity. The long action AICS mags only hold 5 rounds, maximum. The only exception that I know about is the Accurate-Mag 6-round double stack. Please let me know if you know of a source of higher capacity long action mags. The Accurate short action magnum mag (00100-0008) holds 7 rounds. This is a 40% improvement in capacity over a 5-round long action mag!

redneckclimbing:

I've been considering doing a 7mm long range rifle project on the cheap. Though it's not very popular for custom work, I'd like to use a Ruger M77 Hawkeye as the platform. I was even considering using the Gunsite Scout Rifle and avoid the expense of DBM bottom metal, but I don't feel comfortable with a short action for long 180 gr. Berger (or Even 162 gr. Amax) loads. Even with a max COAL of 2.980 inches, which seems to be about as long as you can feed with Alpha mags and similar, it's just too close for comfort for 284 Win, 284 Shehane, 7mm SAUM, 7mm WSM, or 7-08. Quickload helped me to reach this conclusion. Seekins has a 3.1" COAL WSM solution, but it's not AICS and it's only for Remington actions.

So I'll machine my own bottom metal, if I have too, but your wildcat might permit me to save some time and money and use the Ruger GSR after all!

I have Quickoad and Quicktarget. We could work together on this. Let's exchange PMs and email addresses.